The GPU in the Vita is still pretty powerful by mobile standards. It's comparable to the SGX543MP4 found in the iPad 3, while also having to drive far fewer pixels. The Vita uses this extra horsepower to enable anti-aliasing, something we don't really see in the tablet arena yet.
The Vita is a good console, Sony has just been making bad decisions with it. Card locking and expensive proprietary storage/accessories are just a few. Everything about the Vita just screams paranoia over anti-piracy.